Sandblast device



Oct. 17, 1939. L. L.. TIRRELL 2,176,577

SANDBLAST DEV-ICE Filed April 3, 1937 2 Sheets-Sheet 1.

L. L. TIRRELI.

sANDBLAsT 15EvIcE Oct. 17, 1939.

Patented Oct. 17, 1939 sANnBLssr nevica Leslie L. Tirrell, BentonHarbor, Mich., assigner to The Hydroblast Corporation, Chicago, lili., a

corporation of Illinois Application April 3, 1937, Serial No.113d,692

4 Clailns.

This invention relates to improvements in sandblast guns and moreparticularly to a sandblast gun that is operated by hydraulic pressure.

In the art of cleaning and abrading, it has been customary to use steamor air as the motive power for projecting the abrasive from a sandblastgun. The use of water or kother liquid, however, is more desirable thanthe use of steam or air since it costs less, prevents silicosis,effectively removes core sand from castings, washes back the usedabrasive to a point where it can be collected and reemployed, avoidsburning the surface being blasted; and provides better vision for theoperator. 'Water or liquid, having higher surface tension and greaterdensity than-air or steam, also provides a more forceful and easilyAcontrolled stream. In the past, the use of water has generally beenregarded as impractical, since a large amount of water has been requiredto project a relatively small amount of abrasive. This is because astream of water projecting from one jet to another through a sandinjection chamber in the gun is not easily penetrated by the abrasiveparticles. Consequently, only a small amount of abrasive is incorporatedinto the liquid stream.

The principal object of this invention is to provide a practical methodfor driving the abrasive particles into the liquid stream. A furtherobject is to provide a method in which a small solid stream of waterunder high pressure can be employed to project a relatively large amountof abrasive. Other objects and advantages willA appear hereafter in thisspecification.

I have found that a very small substantiallysolid stream of water orother liquid when employed under sufciently high pressure, can be kusedto project a relatively large amount of abrasive, provided the abrasivecan be driven into 40 the stream. This I accomplish by so proportioningand shaping the mixing chamber that the abrasive particles mixed withair are rotated at high velocity and are thereby driven into the liquidstream by the resulting centrifugal force. The air in this mixturebecomes incorporated with the water stream and aids the entry of theabrasive particles thereinto in a manner to be described.

For the purposes of illustration, I have shown one form of apparatus inwhich the method may be satisfactorily used. This apparatus is shown inthe accompanying drawings, in which the various parts are alwaysdesignated by the same gg numerals throughout the several views.

Fig. 1 ls a longitudinal sectional view of a gun embodying thisInventiom- Fig. 2 is an elevation of the gun connected to a feeder in asand bucket, the bucket being shown in section; 5

Fig. 3 is a partial sectional view of the sand feeder;

Fig. 4 is a partial sectional View of an alternative sand feeder; and

Fig. 5 is a partial sectional view of another l@ alternative sandfeeder.

Fig. 6 is a fragmentary sectional view of a portion of the gun shown inFig. l and includes a .erresentation of the liquid jet and abrasive parces.

In the drawings, the gun 5 consists of a tube made up of the axiallyaligned sections I0, I2, I4, I6 and It. Within this tube are a nozzle20, ,a chamber 22, a nozzle 24, and a water valve 26.

The nozzle Isof substantially cylindrical 90` section with a taperedaxial hole 28 extending therethrough. 'I'his hole 28 is smallest at theforward end and increases in size gradually as it extends rearwardlyuntil it reaches a point near its rear end from where it flaresoutwardly g5 to the periphery of the nozzle. 'I'his nozzle 20 has anexternal annular ridge 30 that is clamped between the sections I0 and I2of the nozzle casing when they are screwed together,

The nozzle casing consists of the two sections I0 80 and I2 which whenfitted together form a sleeve with an axial hole 32 to iit the nozzle 20and an annular groove 3d to hold the ridge 30, so

. that the nozzle 2@ will not be forced from the gun by the projectedabrasive and water mixture. 85

Behind the nozzle 2l! is the section I4 containing an annular recess 22that is largest at a point near its center and is rounded inwardlytoward bothends, so that it is of less diameter at its ends than in thecenter. 4@

Into the lower side of this chamber 22 the` abrasive is brought throughthe nipple 36, which is connected to the sand hose 38.

Fitted to the rearward side of the section I4 is the bushing I6 providedwith an internal thread into which is fitted the rear nozzle 24.Extending rearwardly through` the bushing I6 is a water passage 42.

The rear nozzle 26 has a cylindrical opening 4d therethrough which conesoutwardly and rearwardly from a point 46 near its center. 'Ilhe externalforward face tof the nozzle 2 substantially continues the curve of thechamber 22, so that the inside surface of the chamber 22 plus 5g thecontiguous surface 68 of the nozzle 26 fe a modlned toroidal surface.

The bushing i6 is joined' at its rearward end to section i8 whichcontains a rearwardly extending recess 52 containing a valve 2@ which isof well known construction; extending obliquely outwardly from therecess 52 is a. water inlet passage 56 provided with a thread 5@ at itsoutward end for attaching a water hose 6d. Near the forward end of thesection i@ is a valve seat t2 against which is forced a valve washer t@when a knob 65 is turned to the right, thereby cutting oif the flow ofwater through the gun.

The sand hose 38 is connected to a feeder @8 which consists oi a sandpipe i@ joined to the hose and extending for an inch or two into somesand 12 in a barrel 18. Fastened to this pipe 1li is a tube 1t which isopen to the air at the top and extends through an opening 11 in the sandpipe 10 at a point near its lower end. The lower end of the tube 16 isapproximately one-half inch from the bottom of the pipe 1t.

Since in operation the part of the tube i6 that is inside the pipe 'i0is cut away in time by the abrasive particles, I prefer to join the twotogether by clamps or friction tape, so that the tube 16 can be easilyremoved from the pipe 1@ and a new tube substituted.

In Figs. 4 and 5 are shown two alternate feeders that may be substitutedfor the above described feeder 6B. Both of these alternate forms have asand pipe connected to the hose 38 to supply sand thereto, and differfrom the feeder 68 only in the manner in which air is mixed with thesand particles.

In Fig. 4 a sand pipe 18 is surrounded by a sleeve 18, the insidediameter of which is somewhat larger than the outside diameter of thepipe 18. The sleeve 19 projects about one-half inch below the end of thepipe i8 and is secured in spaced relation thereto by means of bolts 80,nuts 8| and spacing washers 82, thus providing an annular space 83 forthe passage of air.

In Fig. a sand pipe 85 is provided with a tube 86 open to the atmosphereat the top and which extends downwardly along the pipe 85 and at the endthereof is curved inwardly and upwardly so that the opening 81 of thetube faces upwardly and is about one-quarter inch below the surface ofthe pipe.

When it is desired to operate the apparatus,l

the gun is connected to a relatively high pressure water supply, in thenature of '100. pounds per square inch, and to the sand hose 38. Thefeeder 68 is thrust into the sand 12 about an inch or so.

When the valve 26 ls opened by turning the knob 66, the water owsthrough the chamber 56, around the valve 26, and into the passage 42. Asillustrated in Fig. 6, the water passes through the opening 44 in thenozzle 24 and comes out as a jet moving at great velocity. This -jet ofwater passes through the abrasive injection chamber 22 and the frontnozzle opening 28.

Since the nozzle opening 44 is cylindrical, the

water passing therethrough will encounter con-` siderably more frictionalong the surface than in the center. This friction causes the surfaceof the jet to be retarded with respect to the center, thereby causingthe jet of water to expand as it passes through the chamber 22, andproduce a depression therein and within the sand hose 38. Consequentlyair will ow downwardly through the tube 16 and into the sand pipe 10.This jet of air strikes the sand at the lower end of the pipe andagitates it. The air then ows up atraer? inside of the pipe 1B to thegun, carrying the sand along insuspension. Because of the resistanceoiered to the now of air by the tube 16 and by the weight of the sandparticles in the pipe 10 andA hose 33, the air enters the chamber 22 ina rareed condition.

If the sand feeder shown in Fig. 4 is used, the operation is similar tothat described above, ex-

. cepting that here the .air iiows downwardly are desired, or if thesand must be lifted a greatV distance.

As illustrated in Fig. 6, when the sand and air strike the water streamin the gun, the particles lsuch as 90 are driven forwardly, thenoutwardly,

then rearwardly, and then inwardly, as indicated by dotted arrows Si.This is, the particles travel at a high speed which is dependent upon orproportional to the jet speed and in smoke-rng like manner. Thecentrifugal force produced by this movement of the particles is insubstantially the direction illustrated by the arrows such as 92 anddrives the sand particles into the liquid stream.

Since these abrasive particles are moving much more slowly than thewater stream at the instant of impact, their inertia causes them toresist the accelerating force of the stream. Consequently, as eachparticle strikes lhe jet of water and is accelerated up to jet velocity,it causes a partial vacuum to be formed on the side of the particletoward the front of the gun. The many small vacuum spaces thus formedare in turn lled by the rareed air which has been brought into thechamber 22 along with the sand. As the stream of water continues throughthe chamber 22 these pockets or bubbles of rareed air provide an easilypenetrable surface for additional sand particles, and likewise, sanddrawn into the nozzle 20 along the surface of the jet easily nds its wayinto the central portion of the porous stream. Therefore, as the jet ofwater flows through the chamber 22, it will be seen that abrasiveparticles are incorporated therein both by the centrifugal forcedeveloped and also by the filling of the rarefied air bubbles with theabrasive particles.

From the chamber 22 the homogeneous mixture of water, sand, and rareedair is projected from the nozzle 20 in the form of a jet which is highlyeil'ective in cleaning and abrading operations.

As far as my knowledge goes, past attempts to use water as a motiveforce in an abrading gun have resulted in the failure of the abrasive topenetrate to the center of the stream. This is because the stream ofdense liquid having suri'ace tension and under such high pressurepresents a medium that is rather hard and that is not easily penetratedby the abrasive particles.

In accordance with my invention, and as illustrated in Fig. 6.a smallstream under high pressure is provided, and the chamber 22 is so shapedthat the abrasive particles carried in the rareed air travel at highvelocity in paths similar to those in which particles travel in asmoke-ring. 'I'he centrifugal force acting upon the sand particles byvirtue of their movement throws them into the stream. The stream alsobecomes pene-v trable because of the rareiled` air which is also takenin with the sand, as described above,l to form a homogeneous mixture ofsand, water, and rareiled air in which a small amount of water carries asuitably large quantity of abrasive. 'I'his mixture when projected islhighly eilicient in cleaning and abrading surfaces both because canbe'made therefore while utilizing the inven of its abrasive effect andbecause of the washing A properties of the water.y

While in the foregoing specification, I have given a preferredembodimentof my device and suggested certain pressures as desirable, it will beunderstood that the invention may be em ployedunder various conditionswith changes in pressures to accommo'date the process to differentclasses of work. Also, it will be understood that the dimensionssuggested are forthe purpose of illustration only, and wide variationstion.

The foregoingdetailedfdescription has been" given for the" purpose ofclearness of understanding only, and no unnecessary limitations shoul beunderstood therefrom.

. Having described my invention, what 1' man as new and useful anddesire to protect by Letters Patent is: f y

i1. A method for blast-treating a surface, comprising: passing anon-compressible liquid in a single confined stream and under a highpressure 'through a loading zone and thence to the sur face to beblasted, supplying granular abrasive by suction to said zone,transferring said granular 'abrasive from said zone intona-intimatemixture with said stream, the transference be- .air by the force of thejet 'centrifugal force, and and entrained granular abrasive as a secondhigh 25 vdeveloped by rapidly moving said granular abrasive in vortexrings within the loading zone by the force of lsaid conned stream. 5

2.F The method of admixing abrasive with` a rapidly moving liquid streamcomprising the steps of projecting the liquid stream, mixing abrasiveparticles with air, 4whirling the mixed'` abrasive particles and air ina space surround-jm ing' the projected stream to drive the abrasiveparticles and air into the liquid stream by centrifugal force to form aporous stream, and co1- lecting more abrasive particles in the open lspaces in the porous stream. 15 3. The method of projecting granularabrasive comprising the steps of mixing granular abrasive with'air,projecting water as a high velocity jet, whirling the mixture ofgranular abrasive andin planes passing through the axis of the jet in aconiinedspace l .surrounding said jet and at suiicient speed that thegranular abrasive is thrown into the jet by reprojecting the water`velocity jet.

V4. The method of projecting grammar abrasive comprising the steps ofprojecting a highvelocity jet of fluid carrying medium through a connedspace, introducing a mixture of granular abra- 30 sive and air into thesaid confined space, whirling th'e mixture of granular vabrasive and airwithin the ccnned space by the force of the jet and at a speed dependentupon the speed of the jet, so that centrifugal force throws the granu-35 lar abrasive/into, the :|et, and reprojecting the fluid carryingmedium and entrained granular abrasive as a second high velocity Jet.

' LESLIE

